This video is available on CBS All Access

This segment was originally broadcast on April 6, 2008. It was updated on July 3, 2008.

The name Douglas Feith may not mean much to most Americans, but to students of the Iraq war and historians already studying it, he is one of the main architects.

From 2001 to 2005, Feith was under secretary of defense for policy and the No. 3 man at the Pentagon, intimately involved both pre-war strategy and post-war planning. His boss, Defense Secretary Donald Rumsfeld, called Feith one of the most brilliant individuals in government but he has also been a lightning rod for criticism and a magnet for blame.

As correspondent Steve Kroft first reported in April, in his memoir, which has been called the first insider account of decision making in Iraq, Feith defends much and apologizes for very little. But he offers some unusual insights about the path to war.

Asked why the United States invaded Iraq, Feith tells Kroft "The President decided that the threats from the Saddam Hussein regime were so great that if we had left him in power, we would be fighting him down the road, at a time and place of his choosing."

If Feith doesn't look or sound much like a warrior that's because he isn't; he's an intellectual, a hawkish, neo-conservative defense policy wonk, who occupied one of the top rungs on the Pentagon ladder, playing a key role in shaping the military's response to 9/11 and the decision to go to war with Saddam Hussein.

Asked why the decision was made to go after Saddam Hussein after 9/11, when even then, the United States government realized Saddam didn't have anything to do with the attacks, Feith answers, "What we did after 9/11 was look broadly at the international terrorist network from which the next attack on the United States might come. And we did not focus narrowly only on the people who were specifically responsible for 9/11. Our main goal was preventing the next attack."

Kroft follows up, asking, "So you're saying you didn't think it was that important to go after the people who were responsible for it -- more important to go after people who weren't responsible for it?"

"No," Feith explains, "I think it was important to go after the people who were responsible for 9/11. But it was also important to disrupt the international terrorist networks and prevent whatever plans there were for follow-on attacks."

Kroft points out that using those standards, the U.S. could have invaded North Korea or Syria or Iran.

Feith concedes the point, but counters that Iraq was a special case, in large part, because of Saddam's record.

Feith says Saddam had already attacked Kuwait, Iran, Israel and Saudi Arabia; that he had defied the United Nations, evaded economic sanctions, used weapons of mass destruction on his own people and had the know-how, if not the wherewithal, to build a nuclear weapon. Feith believes the U.S. invasion was justifiable as an act of self-defense. In his book, he used the term "anticipatory self-defense."

"In an era where WMDs can put countries in a position to do an enormous amount of harm," he tells Kroft, "the old of idea of having to wait until you actually see the country mobilizing for war doesn't make a lot of sense."